Electrochemical detection coupled to high pressure liquid chromatography is a means for determining relative or absolute quantities of readily oxidizable materials in solution. The high sensitivity of the method makes it comparable to radioactive tracer methods for determination of minute quantities.
At the level of picomoles or less per sample the presence of a high concentration of salts, proteins, or other extraneous solutes may interfere with the detection. This is a problem particularly with biological fluids, which usually cannot be injected directly into a high pressure liquid chromatography (HPLC) column equipped with a coulometric detector. A preliminary separation procedure is desirable. This typically consists of column chromatography, perhaps involving an ion exchange resin. This separation increases the number of manipulations required per sample and complicates the rapid determination of a large number of samples.
Another limitation of current methodology is that the compound of interest must contain an electroactive (oxidizable or reducible) group such as a phenol group. Many components of interest in biological fluids cannot at present be measured by electrochemical detection, because they are not sufficiently electroactive. The biogenic amines, histamine, for instance, which is an important chemical messenger in the body and one of the mediators of anaphylactic reactions, are chemicals which cannot be detected directly. A chemical derivatization method for such non-electroactive amines, based on an o-phthalaldehyde reaction, has been suggested, but this approach suffers from a reversibility of the derivatization reaction and a low sensitivity.